1. Technical Field of the Invention
Handtools with a pneumatic linear vibrating drive are known. They are used to saw, grind, polish, file and cut workpieces. The vibrating drive comprises a piston which is mounted displaceably in the handle and has a piston rod, to the front of which a tool holder is attached. The piston is driven by a flutter valve which alternately connects a cylinder chamber to the feed pressure which is supplied via a manually actuated pilot valve and to an exhaust air duct.
2. Prior Art
EP-A-89 311 has disclosed a vibration damper for such a handtool. A damper mass is mounted in such a manner that it can be displaced in the longitudinal direction in the casing and is supported with respect to the casing by means of rubber springs. However, this vibration damper increases the length of the structure and is frequency-dependent.
Moreover, DE-A-32 12 701 has disclosed a pneumatic hammer as described in the preamble of Claim 1. The hammer has a tool casing with a linear vibrating drive. The latter comprises a motor casing which can be displaced in the longitudinal direction in the tool casing. A piston with a piston rod is inserted in a coaxial boring in the motor casing, the front end of which piston rod strikes a tool which is mounted displaceably in the tool casing. A flutter valve is incorporated in the motor casing. Compressed air is applied to the flutter valve via an annular chamber which surrounds the motor casing and via a pilot valve. The flutter valve alternately connects the annular chamber to the two cylinder chambers on either side of the piston. The piston alternately opens the connection between the cylinder chambers and an exhaust air duct. A prestressed compression spring exerts a forwardly directed load on the motor casing. This design requires a relatively large diameter of the tool casing. The piston has a relatively small active area in the direction of return travel, since the return travel merely involves xe2x80x9cdrawing backxe2x80x9d for the next impact, and there is no need for any work to be output.
The invention is based on the object of providing a handtool of the type described in the introduction which allows efficient vibration damping combined with a short structure and a small external diameter.